Effects of Earthquakes
Earthquakes are among the most
powerful and destructive natural events on Earth. Their effects can be
categorized into direct effects (caused directly by the
shaking) and indirect effects.
DIRECT EFFECTS
These occur immediately due
to ground movement during an earthquake.
Ground Effects
- Ground Shaking
- Ground Cracking
- Ground Lurching
(sudden sideways ground movement)
- Differential Ground Settlement
(uneven sinking)
- Soil Liquefaction
(soil loses strength)
- Lateral Spreading
(ground slides horizontally)
- Landslides
- Rockfalls
Structural Effects
- Vibration of Structures
- Falling Objects
- Structural Damage
- Structural Collapse
INDIRECT EFFECTS
These occur because of
secondary hazards triggered by the earthquake.
- Landslides
(triggered after shaking)
- Tsunamis
- Seiches (oscillating lake
waves)
- Avalanches
- Rockfalls
(delayed)
- Floods (dam or
embankment failures)
- Fires (gas line breaks,
electrical faults)
- Toxic Contamination
(industrial chemical releases, sewage leaks)
Damage to Buildings
Extensive structural damage is
suffered by buildings during earthquakes. Seismic vulnerability of structures
varies as a function of construction materials and earthquake action- resisting
system employed.
Typical Damage to Building
Structures:
Masonry & Reinforced Concrete (RC) Structures
Beams
- Shear failure
- Concrete cover spalling
- Reinforcing bar buckling
Columns
- Cracking and crushing
- Concrete cover spalling
- Rebar buckling and pull-out
- Flexural and shear failure
- Short-column effect damage
Connections
- Cracking and crushing
- Rebar buckling and pull-out
- Shear failure
Structural Walls & Infills
- X-shaped (diagonal) cracking
- Crushing
- Rebar buckling
- Overturning, rocking, sliding
Foundations
- Settlement
- Rebar pull-out
- Rocking, sliding, uplifting
Frames (Whole Structural
System)
- Soft/weak storey collapse risks
- Large residual deformation
- Diaphragm and connector distress
- Pounding with adjacent buildings
- Rocking, uplifting
- Parapet and chimney failure
Steel & Composite (Steel–Concrete) Structures
Beams
- Flange and web yielding
- Local buckling
- Brittle fracture
Columns
- Flange yielding
- Local buckling
- Brittle fracture
- Splice failure
- Member buckling
Braces
- Local and overall buckling
- Brittle fracture
Connections
- Yielding
- Local buckling
- Brittle fracture
- Weld cracks
- Excessive panel deformation
- Bolt rupture
Foundations
- Bolt anchorage rupture
- Weld cracks and fractures
- Pull-out failures
- Excessive base-plate deformation
Frames (Whole Structural
System)
- Soft/weak storeys
- Excessive residual deformation
- Distress in diaphragms/connectors
- Pounding
- Uplifting
Damage to Lifelines
Lifelines are those services
that are vital to the health and safety of communities and the functioning of
urban and industrial regions. These include electric power, gas, water and
wastewater systems. Infrastructures, such as transportation systems (highways
and railways), bridges, ports and airports are also classified as lifelines.
Damage to lifelines imposes devastating economic effects on the community. Their
seismic performance affects emergency response, short- term and long - term
recovery. Broken gas and power lines are serious threats to safety, largely
because of risk of fire and explosions. The lack of water also inhibits
firefighting efforts. Leaks and rupture of wastewater systems may lead to toxic
contamination.
Typical Damage to Lifelines
1. Highways and Railways
- Bending and shear failure of reinforced
concrete piers
- Local and overall buckling of
steel/composite piers
- Brittle fracture
of welded components
- Pounding and unseating
at hinge seats and deck supports
- Cracks, gaps, and settlements
in pavements
- Rails bending or rupturing
- Train derailments
2. Gas and Electric Power Systems
- Cracks and ruptures in gas pipeline
networks
- Brittle fracture in porcelain
components of high-voltage substations
- Switching system failures,
crane and tank damage in power plants
- Disruption of electric power supply
- Fires and explosions
caused by gas leaks
- Malfunction or collapse of transmission
towers
3. Water and Waste Systems
- Breakage and leaking
of water/waste pipelines
- Sloshing damage and suction failure
in metal storage tanks
- Elephant-foot buckling
and shell buckling of tanks
- Cracks and leaks in concrete basins
- Malfunctioning process equipment due to ground
settlement or rocking
4. Communication Systems
- Damage to electronic switching systems
- Damage to telephone lines
- Structural damage to telephone system
buildings
- Malfunctioning of computer networks
- Malfunctioning and collapse of transmission
towers